In the sale and distribution of liquefied petroleum fuel gas (L.P. Gas) to individual customers it is conventional for a distributor to use stationary, above ground bulk storage tanks, as large as sixty thousand gallons, to store the highly volatile and inflammable liquid under substantial vapor gauge pressure and then distribute it to customers by delivery truck tanks that are filled repeatedly from the storage tanks under said vapor pressure through detachable liquid supply and vapor return conduits which include flexible hoses detachably connected to the truck delivery tank. These conduits are permanently connected to the bulk storage tanks and have automatic cut off flow control valves at the outlets to the hoses and shut off valves at the free ends of the hoses connectible to truck tanks which in turn have back check valves.
It is desirable that the conduits include quite flexible hoses to accommodate a random and quick positioning of a tank truck for rapid connection thereto and filling. Preferably the transfer hoses are short, approximately ten feet long (3 meters), and are one and one half inch or larger in diameter for strength and ease of handling, and also for rapid filling while, for safety, minimizing the volume of liquefied gas present at any given time in the hoses between the tanks. The liquefied gas is forced by the liquefied gas pressures or by pumps through the liquid hose at a high rate of flow to minimize tank filling time and maximize customer deliveries.
Aside from maintaining the handling and filling equipment in acceptably safe condition, an ever present random danger conventionally exists in which, for any one of several reasons, a delivery truck driver receiving L.P. Gas will occasionally drive his replenished truck away while the hoses are still connected between the truck tank and storage tank. This ruptures the hoses under substantial tension and gas pressure forces, and generally after such a hose rupture, there is substantial pressurized spillage of liquefied gas that rapidly creates a highly dangerous fire hazard regardless of the automatic closing of safety flow-check valves after a break. Substantial amounts of vaporizing gas escape before conventionally arranged valves are effective. Automatic outflow cut-off transfer valves have been used such as described and claimed in Application Ser. No. 708,128, now Billington et al, U.S. Pat. No. 4,099,551, where a trip cut-off cord is connected to the truck which trips a valve by unlatching a dog that supports a spring for closing check valve in the outflow to the hose. Many times it has been found that the cord is not attached to the truck during filling operations.
In the present invention, the valves are closed before a rupture occurs in either hose and at most any escaping gas would be only that in the filler hose. The check valve in the invention closes in the direction of outflow. It also has means to close the valve if a fire may already have been started from sparks or any one of several other reasons, thereby confining spillage to the short hose contents which if ignited would quickly burn out with minimal escape of gas with a fuse metal release also assuring automatic closing of a dispensing outlet valve. These are improved safety steps.
One of the objects of the invention is to compel the followance of the proper sequence of the truck tank filling procedure in a way which automatically prevents any hazardous spillage if there is inadvertant drive away without disconnection and prevents any further use without attention and repair.
Another object of the invention is to control and limit any escape of hazardous material to only a readily dispersible known amount and confine any damage to equipment that is easily restored or replaced.
Another object is to assure good inspection, testing and upkeep of frangible safeguards provided for the ultimate prevention of dangerous break-away spillage and fires.
A further object includes safeguarding truck filling equipment against damage of any parts other than a quickly replaceable preassembled hose unit rigidly supported against movement at its storage tank end.
Other and further objects include the inhibition of liquid transfer except by personnel present if automatic equipment might be defective or improperly handled.
Moreover, the safety cut off control can serve as an additional manual shut off control when the delivery tank is filled to its proper level. Thereupon, with the shut off accomplished the setting of all controls and connections can be finalized for disconnecting the truck tank safely from the storage supply tank.
These being among the objects of the invention, other and further objects will appear in the drawings and description that follows.